Method and device for a fin-stabilized base-bleed shell

Abstract

The present invention relates to a method and a device relating to shells with deployable fins and which are fired from large caliber guns into ballistic trajectories, for preventing the propellant gas pressure in the barrel during firing from directly or indirectly deforming the said fins ( 9-13 ). The type of fins that the present invention primarily relates to are those that are deployed on command in order to fin-stabilize the shell. Usually such fins are protected prior to deployment by an ejectable fin protector ( 19 ). To prevent this fin protector from being deformed and consequently impeding fin deployment or degrading fin functionality, the present invention proposes that all unoccupied space inside the said fin protector be filled with an inert, noncombustible, non-glutinous substance ( 32 ) of low compressibility and very low inherent strength. This substance, which completely fills the space inside the fin protector around the fins ( 9-13 ), will detach from the fins after fin deployment as a result of mainly centrifugal forces, but until that point in time will effectively prevent all undesirable deformation of the fin protector and thereby indirectly of the fins. Until ejected the fin protector ( 19 ) is thus fully sealed.

We claim:  
     
       1. A method for a shell that is fin-stabilized at least during a final part of a flight trajectory of said shell, for preventing deformation of deployable fins incorporated in a tail unit of said shell, said method comprising the steps of: 
       providing a shell that is fired from a gun barrel where the shell is subjected to the full effect of propellant gas pressure in the gun barrel during a firing phase;  
       protecting said fins during a firing phase of said shell by a fin protector with limited wall thickness, said fin protector surrounding a rear section of said shell and being ejected at a point in time for fin deployment;  
       designing said fin protector to join an external surface of said shell at a sealed interface, said fin protector being separable from said shell at said interface; and  
       filling a ring-shaped space, within said fin protector and not occupied by said fins, completely with an inert, non-combustible, non-glutinous substance of low compressibility and very low inherent strength.  
     
     
       2. The method of  claim 1 , wherein said substance has such properties that after fin deployment none of said substance is able to remain on the fins or a body of the shell. 
     
     
       3. The method of  claim 1 , wherein said substance comprises a bi-component, curing silicone with low inherent strength in a cured state. 
     
     
       4. The method of  claim 1 , wherein said substance comprises a fluid. 
     
     
       5. The method of  claim 4 , wherein said fluid is water. 
     
     
       6. The method of  claim 1 , wherein said substance comprises a thixotrope fluid with low inherent strength and low compressibility. 
     
     
       7. A shell that is fin-stabilized at least during a final part of a flight trajectory of said shell including a device for preventing deformation of deployable fins incorporated in a tail unit of said shell, said tail unit being subject to a full effect of a propellant gas pressure in a barrel used for firing said shell, comprising: 
       a shell comprising deployable fins incorporated in a tail unit;  
       an ejectable fin protector with limited wall thickness, said fin protector being insufficient to independently resist said gas pressure, and being formed as a sleeve open at a front location but completely closed at a rear location;  
       said fin protector surrounding said tail unit until a point in time when said fin protector is ejected and said fins are deployed, and being joined with a gas-tight but breakable seal with a body of said shell; and  
       a ring-shaped free space within said protector, not occupied by said fins, said free space being completely filled with an inert, non-combustible, non-glutinous substance of low compressibility and very low inherent strength.  
     
     
       8. The shell of  claim 7 , wherein said fin protector is permanently joined to a base-bleed unit of said shell so that said fin protector and said base-bleed unit are ejected together. 
     
     
       9. The shell of  claim 7 , wherein a base-bleed unit of said shell and said fin protector form a combined unit, said base-bleed unit being located in the center of said fin protector so that a ring-shaped space is formed between said base-bleed unit and said fin protector, said space being initially occupied by said tail unit and said fins, and said fins initially being retracted convexedly around an outer surface of said tail unit. 
     
     
       10. The shell of  claim 7 , wherein said fins are made of sheet-metal material with very high elasticity and long-term form memory, each fin being bent around its own hinge pin immovably secured longitudinally in said shell body, each said hinge pin incorporating two diametrically opposite longitudinal locking flats radially located relative to a cross-section of said shell, wherein said bending of each fin around each hinge pin is such that the fin pinches the hinge pin. 
     
     
       11. The shell of  claim 7 , wherein said substance comprises a bi-component, curing silicone with low inherent strength in a cured state. 
     
     
       12. The shell of  claim 7 , wherein said substance comprises a fluid. 
     
     
       13. The shell of  claim 12 , wherein said fluid is water. 
     
     
       14. The shell of  claim 7 , wherein said substance comprises a thixotrope fluid with low inherent strength and low compressibility.